Fork 3 processes, one for each server. Start timers for each of them, whichever reports the least amount of time lapse is your quickest.

This will give you an accurate picture of which server is, not only initially fastest, but also maintains bandwidth for your connections.

pings, traceroute, and tools like that can give you a quick idea if that is all you want, however timing the actual process will give you actual performance. Especially in this case where you are redirecting traffic. Doing a simple HTTP get on a known file size and timing the transaction from start to finish should accomplish what you need.

"Nothing is sure but death and taxes" I say combine the two and its death to all taxes!